Characteristics of methanogens and methanotrophs in rice fields: a review

Methane is the second most important greenhouse gas after carbon dioxide (CO2) with a global warming potential 25 times more than CO2. Rice fields are one of the main anthropogenic sources for methane and responsible for approximately 15-20% of the annual global methane efflux. Methanogens and methanotrophs are two microbial communities which contribute to the biogeochemical methane cycle in soil by producing and oxidizing methane, respectively. In fact, the total methane emission from rice soil is the balance between methanogen and methanotroph activities. Methanogenic archaea are more active in highly reduced conditions and anoxic soils. However, methanotrophs are more active in oxic soils. These microorganisms have been studied frequently in different soils from natural wetlands to rice fields. This article has mainly focused on the characteristics of methanogens and methanotrophs in a rice soil ecosystem with the objective of deriving solutions the high level of methane emissions from paddy fields

Evaluation of methane oxidizer bacteria in the rice soil in Malaysia

Methane is known as a powerful greenhouse gas due to its global warming potential (GWP = 21). Rice fields are methane producers because of the flooding irrigation system. Two microbial communities are involved in methane cycle in the soil including methanogens and methanotrophic bacteria which are responsible for methane production and methane oxidation respectively. Methanotrophic bacteria as aerobic unicellular microorganisms dominantly exist in soil oxic area (e.g. surface of the soil and the rhizosphere). These microorganisms can regulate the methane emission from rice soil. This experiment applied PCR-DGGE to detect methane oxidizer bacteria (MOBs) within the rice soil from two depths 0-5 cm and 5-10 cm in different rice growth stages and cultivation systems. Consequently, several MOBs from type I and type II could be identified. However, type I was detected in depth of 0-5 cm and drained condition rather than 5-10 cm and flooding condition

Methane emission from paddy soil in relation to soil temperature in tropical region

Methane (CH4) is 21 times more powerful as a greenhouse gas than carbon dioxide. Wetlands including flooded paddy fields are one of the major sources for this gas. Paddy fields are responsible for producing 25 to 54 Tg of CH4 annually. Methane emission rate could be affected by several factors such as irrigation pattern, fertilizer type, soil organic matter and soil temperature. Among them, soil temperature is a determining factor which deserves to be investigated. This study performed with the aim of understanding the effect of soil temperature on the methane emission rate from paddy soil in a short period of time (hourly) and long term (during rice growing season). The results of this study suggest that soil temperature could control the amount of methane emission and there is a positive and strong correlation in both soil temperature and methane emission pattern in short period of time. However, in case of long term trend, other factors such as water management and plant age decreased this correlation from 0.768 to 0.528

Effects of cultivation system and temperature on methane emissions, water consumption and methane-oxidizer bacteria communities in paddy soil

Methane (CH4) is a potent greenhouse gas with a global warming potential of 25 times more than CO2. Paddy fields are important sources of methane and contribute in approximately 15–20% of the annual global methane efflux. Methanogens and methanotrophs are two microbial communities contribute in the biogeochemical methane cycle in soil by producing and oxidizing the methane respectively. In fact, the total methane emission from rice soil is the balance between methanogens and methanotrophs activities. Methane emission rate could be affected by several factors such as irrigation pattern, fertilizer type, soil organic matter and soil temperature. Between them, soil temperature is a determining factor which deserves to be investigated. Also, cultivation systems can affect the methane emission by their different water management and practices. One of the cultivation methods is the System of Rice Intensification (SRI) which includes Original SRI and blong-Triangular SRI. Therefore, this study was performed with the main aim of introducing a sustainable rice production system with less contribution to global warming and more productivity. Therefore, the effect of soil temperature and different cultivation systems on the methane emission rate from rice soil was studied. In addition, identification of methane-oxidizer bacteria (MOBs) was conducted in two rounds. Static chamber method has been applied to evaluate the influence of two SRI methods and conventional method on methane emission. As a result,conventional method showed the highest total methane flux with emitting of 26.4 g CH4 m-2 compared to original SRI treatments and triangular pattern with 7.7 g CH4 m-2 and 8.9 g CH4 m-2 respectively. The pattern of water management was the most influencing factor led to lower methane emission in SRI treatments. SRI treatments produced higher yield than the conventional method so that original SRI produced 6.98 and 7.00 ton ha-1, oblong-triangular SRI yielded 7.08 and 7.01 ton ha-1 at first and second round respectively. On the other hand, conventional method presented 6.74 and 6.80 ton ha-1 grain yield at first and second round respectively. Besides, more than 40% water saving was observed in original and oblong-triangular SRIs while higher water productivity including 7.93 and 7.86 kg ha-1 mm-1 were recorded in these cultivation systems compared to conventional method with 4.49 kg ha-1 mm- 1. This could be a promising result toward a sustainable rice production. Moreover, soil temperature showed positive correlation with methane emission both in daily measurements (0.768) and during rice growth season (0.528). However,factors such as water management and plant age decreased this correlation during growth season. Furthermore, this experiment applied PCR-DGGE to detect MOBs within the rice soil from two depths between 0 to 5 and 5 to10 cm in different rice growth stages and cultivation systems. Consequently, several MOBs from type I and type II have been identified. However, type I was detected at 0-5 cm depth and drained condition rather than 5-10 cm depth and flooding condition. Both systems of rice intensification (SRI treatments) were revealed to provide stimulating condition for MOBs (Esp. Type I) compared to conventional method because of aerating the soil alternatively. Besides, SRIs showed higher diversity of MOBs in comparison with Conventional method. SRIs reduced the methane emission by affecting the MOBs' communities. In this regard, SRIs provided favourable condition for type I MOBs to be active and oxidize more portion of produced methane in the soil before being released into the atmosphere. Consequently, SRIs could succeed in methane emission mitigation from paddy soil while they produced more grain yield and represented less water usage. As a conclusion, this study can introduce SRIs as green cultivation systems for a sustainable rice production

Comparison of Methane Emission from Conventional and Modified Paddy Cultivation in Malaysia

AbstractMethane (CH4) is a potent greenhouse gas (Global Warming Potential = 25). Flooded rice fields are main sources for methane. Finding solutions to suppress the methane emission seems necessary toward a sustainable rice production. This study's aim is to assess the methane emission from some modified rice cultivation systems in Malaysia. Three cultivation methods including, two modified cultivation systems (MC) and conventional method (C) were studied. Consequently, the maximum methane emission was significantly lower in MCs (3.15 and 3.29mg CH4 m-2 d-1) compared to C (8.91mg CH4 m-2 d-1). Irrigation pattern and plant density were the key factors

Survival rate of mangroves: A proxy to assess ecosystem health

2046-2053Survival rate of mangroves is highly species-specific, which significantly varies between sites. It is observed that survival rate of Sonneratia apetala, Aegiceros corniculatum, Bruguiera gymnorrhiza, Xylocarpus granatum, Nypa fruticans, Heritiera fomes and Derris trifoliate is more in the western sector compared to the central sector of Indian Sundarbans. However, a completely reverse picture with higher survival percentage in the hypersaline central sector is observed for species like Avicennia marina, Avicennia alba, Avicennia officinalis, Acanthus ilicifolius, Excoecaria agallocha, Phoenix paludosa, Ceriops decandra, Rhizophora mucronata and Aegialitis rotundifolia. Salinity seems to be the major driver for mangrove survival. Survival percentages of mangroves seedlings and their transformation into adult forms can be a potential indicator of ambient environment particularly in context to salinity. Such approach can be of importance in the ecosystem health monitoring programme preferably for regions like Indian Sundarbans, where significant spatial variation of salinity exists

Inter-annual variation of salinity in Indian Sundarbans

410-415Using secondary data coupled with real time data, inter-annual variation of surface water salinity in three sectors (western, central and eastern) of Indian Sundarbans during 1984-2013 was studied. Salinity of the aquatic system in the present deltaic complex, situated in the inshore region of Bay of Bengal is primarily regulated by anthropogenic factors (like barrage discharge, run-off from the adjacent landmasses etc.) and natural factors (like siltation, plate tectonics etc.). Surface water salinity has decreased by 0.63 and 0.86 psu per year in the western and eastern sectors respectively, whereas in the central sector, it has increased 1.09 psu per year. Another important objective of the study is to investigate the future salinity (in 2043, 30 years after 2013) in the three sectors of the deltaic complex considering the present data set of 30 years as the baseline. Our forecast through exponential smoothening method reveals an alarming hypersaline environment in the central Indian Sundarbans

Effect of cultivation system on the methane emission from rice soil

Methane (CH4) is a potent green house gas and second in importance after carbon dioxide (CO2) with a global warming potential of 25 times more than CO2. Paddy fields are important sources of methane and contribute in approximately 15–20% of the annual global methane efflux. Cultivation systems can affect the methane emission by their different water management and practices. One of the cultivation methods is the system of rice intensification (SRI). Considering the water management system and the plant density, in this method less methane is expected compared to conventional cultivation method. Consequently, current study has been done to evaluate the influence of two SRI methods on methane emission. For this purpose, closed chamber applied to measure methane emission. As a result, conventional method showed the highest total methane flux with emitting of 26.4 g CH4 m-2 compared to original SRI treatments and triangular pattern (7.7 g CH4 m-2 and 8.9 g CH4 m-2). The pattern of water management was the most influencing factor lead to lower methane emission in SRI treatments. In addition, SRI treatments produced higher yield than the conventional method. This could be a promising result toward a sustainable rice production

Rice cultivation system with less water consumption for sustainable future

Rice is a main food for about one third of the world’s population. Besides, the demand for this crop is anticipated to rise with growing population of the world. Increasing the rice cultivation area can be a fulfillment to hit adequate rice production. Rice crop is mostly produced by conventional method with flooding the soil. Consequently, a remarkable amount of water is used for rice production. This fact emphasizes the necessity of finding a water-saving cultivation system concerning a sustainable future. Current two-round research studied different irrigation systems for rice under different cultivation methods including, original system of rice intensification (SRI), oblong-triangular system of rice intensification and conventional method in relation to water savings. Consequently, more than 40% water saving was observed in SRIs while higher water productivity recorded in these cultivation systems (> 7 kg ha-1 mm-1) compared to conventional method (> 4 kg ha-1 mm-1)